JP2009248399A - Head substrate, recording head, head cartridge, and recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a head substrate which enables good recording even when an environmental temperature, a recording duty and a recording head itself are different, and to provide a recording head, a head cartridge, and a recording apparatus using the recording head. <P>SOLUTION: The head substrate has the following configuration. That is, the head substrate has a plurality of heaters, a constant current source which generates a constant current for driving these heaters, and a reference current generating circuit which generates a reference current for generating the constant current. Moreover, the head substrate is equipped also with a MOSFET which drives the plurality of heaters by the constant current obtained by driving the constant current source according to the reference current, and a switch which regulates a time when the reference current is generated. An opening and closing time of the switch is enabled to be controlled from outside. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a head substrate, a recording head, a head cartridge, and a recording apparatus. In particular, the present invention relates to a head substrate, a recording head, a head cartridge, and a recording apparatus that are used to perform recording in accordance with, for example, an ink jet method and have a circuit for driving by applying a predetermined current to a heater by a constant current method. .

  Conventionally, ink jet recording is performed in which thermal energy is generated by a heater disposed in a nozzle of a recording head, ink is foamed by using the thermal energy, and ink is ejected from the nozzle by the foaming. The head is known. Hereinafter, the ink jet recording head will be referred to simply as a recording head.

  In recent years, an ink jet recording apparatus using this recording head has been required to have high speed and high definition. For this reason, the recording head has a higher density and more nozzles mounted. When driving the heater in the recording head, it is required to simultaneously drive as many heaters as possible at high speed from the viewpoint of recording speed.

  Usually, a large number of heaters and their drive circuits are formed on the same semiconductor substrate (hereinafter, this substrate is referred to as a head substrate). For this reason, a MOS-type semiconductor process is used for forming the heater drive circuit, which allows the device to be denser and more compact than the conventional bipolar semiconductor process, has a simple manufacturing process, and is low in cost. .

  As a new heater driving method corresponding to such a high-speed recording and MOS manufacturing process, a heater driving method using a predetermined current is proposed in Patent Document 1, Patent Document 2, and the like.

  FIG. 13 is a diagram showing a configuration of a heater driving circuit of a recording head proposed in Patent Document 2. In FIG.

  As apparent from FIG. 13, the heater driving circuit includes a reference voltage circuit 105, a voltage / current conversion circuit 104, and a current source block 106. The current source block 106 includes m heater groups that accommodate x heaters. Although not shown, one recording head includes n current source blocks. Accordingly, one recording head is provided with a total number of (x × m × n) heaters.

The reference voltage circuit 105 generates a reference voltage V _ref that serves as a reference for the voltage-current conversion circuit 104. The voltage-current conversion circuit 104 performs conversion from voltage to current based on the reference voltage V _ref from the reference voltage circuit 105, and generates a reference current I _ref from the reference voltage V _ref .

Based on the reference current I _ref generated by the voltage-current conversion circuit 104, a reference current generation circuit (not shown) generates a plurality of reference currents proportional to the reference current I ref . Each of these reference currents is supplied to n current source blocks.

Then, constant currents Ih1 to Ihm proportional to the reference current supplied to the constant current sources are output from the constant current sources 103 _{1 to} 103 _m in each of the n current source blocks with reference to the reference currents IR1 to IRn.

As shown in FIG. 13, the current source block 106 includes (x × m) heaters, the same number of switching elements 102, and constant current sources 103 _{1 to} 103 _m for m groups. . In FIG. 13, in order to individually refer to the (x × m) switching elements 102, a suffix _ij is added to the reference number. Here, i = 1 to m and j = 1 to x. Hereinafter, when referring to the entire switching element 102, the suffix is omitted.

The switching element 102 is controlled to short-circuit and open current between terminals by a control signal from a control circuit of the recording apparatus main body. The (x × m) heaters 101 and the switching elements 102 are composed of m groups each accommodating x pieces. In each group, the heaters 101 _{11 to} 101 _mx and the switching elements 102 _{11 to} 102 _mx for driving control of the heaters are connected in series. The power supply side terminals in each group are commonly connected to the power supply line 110, and the ground side terminals are commonly connected to the GND line 111 via a constant current source. In FIG. 13, in order to individually refer to the m groups, the reference numbers are suffixed to 106-1, 106-2,... 106-m. However, when referring to the entire m groups, reference numeral 106 is used, and the suffix is omitted.

Output terminals of the constant current sources 103 _{1 to} 103 _m provided in each of the _m groups 106 are connected to a common connection end of each group 106 in which the heater 101 and the switching element 102 are connected in series. The drive control of the current to the heater is executed by turning on / off the switching elements 102 in each group by a control signal. Then, the output currents Ih1 to Ihm of the constant current sources 103 _{1 to} 103 _m provided for each group are supplied to a desired heater.

In an actual recording head, a plurality (n) of current source blocks 106 having the same configuration are arranged, and the heater driving operation in each current source block 106 is the same as described above. In this way, by performing the same operation on the n current source blocks 106, any of the (x × m × n) heaters is driven to generate heat.
JP 2004-181678 A JP 2004-181679 A

  However, the above conventional example has the following problems.

(1) Discharge instability and discharge failure in a low temperature environment When the temperature of the environment where the recording device is installed is extremely low (for example, 10 ° C. or less), the viscosity of the ink rises and discharge becomes unstable, which is the worst. In this case, ejection failure occurs.

(2) Difference in Head Temperature Rise Characteristic Due to Recording Duty There is a difference in the temperature rise characteristic of the head substrate between recording a high density image and recording a low density image, and the ink discharge state is different. For this reason, dot formation for a high-density image is different from dot formation for a low-density image, and as a result, image quality may deteriorate.

(3) Head temperature rise difference due to set current value difference of each head substrate Variation in electrical resistance of recording element (heater) occurs due to manufacturing variation of head substrate. For this reason, if a predetermined thermal energy is generated by the recording element, the value of the current flowing through the recording element must be changed. For this reason, since the reference current (hereinafter, set current value) that is the basis of the current supplied to the recording element is changed for each recording head, the amount of heat generated by the reference current generating circuit differs depending on each head substrate. Difference in temperature rise occurs. Accordingly, when the recording head is changed, density unevenness or the like occurs in the recorded image, resulting in a difference in color.

  The present invention has been made in view of the above conventional example, and incorporated a head substrate capable of good recording even when the ambient temperature, recording duty, and recording head itself are different, a recording head using the substrate, and the recording head. It is an object to provide a head cartridge. Another object of the present invention is to provide a recording apparatus using the recording head.

  In order to achieve the above object, the head substrate of the present invention is configured as follows.

  That is, a plurality of heaters, a constant current source that generates a constant current used to drive the plurality of heaters, a reference current generation circuit that generates a reference current for generating the constant current, and the reference current generation A switching element for driving the plurality of heaters by the constant current obtained by driving the constant current source according to a reference current generated in a circuit; and a switch for defining a time for generating the reference current. An opening / closing time of the switch is controlled from the outside, and the head substrate is provided.

  According to another invention, a recording head using the head substrate having the above-described configuration is provided.

  According to still another aspect of the invention, there is provided a head cartridge that integrally includes the ink jet recording head and an ink tank that stores ink to be supplied to the recording head.

  According to still another aspect of the invention, there is provided a recording apparatus that performs recording by ejecting ink onto a recording medium using the ink jet recording head or the head cartridge having the above configuration.

  Therefore, according to the present invention, by changing the time for generating the reference current in accordance with, for example, the detected temperature, the duty for recording, and the characteristics reflecting the manufacturing variation of the recording head, the reference current generating circuit The calorific value can be adjusted. Accordingly, the head substrate is appropriately heated, the temperatures of the head substrate and the recording head are stabilized, and good recording can be performed regardless of the temperature, duty, and individual differences of the recording head.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, “recording” (sometimes referred to as “printing”) is not limited to the case of forming significant information such as characters and graphics, but may be significant. It also represents the case where an image, a pattern, a pattern, etc. are widely formed on a recording medium, or the medium is processed, regardless of whether it is manifested so that humans can perceive it visually. .

  “Recording medium” refers not only to paper used in general recording apparatuses but also widely to cloth, plastic film, metal plate, glass, ceramics, wood, leather, and the like that can accept ink. Shall.

  Further, “ink” (sometimes referred to as “liquid”) should be interpreted widely as in the definition of “recording (printing)”. Therefore, by being applied on the recording medium, it is used for formation of images, patterns, patterns, etc., processing of the recording medium, or ink processing (for example, solidification or insolubilization of the colorant in the ink applied to the recording medium). It shall represent a liquid that can be made.

  Furthermore, unless otherwise specified, the “nozzle” collectively refers to an ejection port or a liquid channel communicating with the ejection port and an element that generates energy used for ink ejection.

  The printhead substrate (head substrate) used below does not indicate a simple substrate composed only of a silicon semiconductor, but indicates a configuration provided with elements, wirings, and the like.

  Furthermore, “on the substrate” not only indicates the head substrate, but also indicates the surface of the head substrate and the inside of the element substrate near the surface. In addition, the term “built-in” in the present invention is not a word indicating that each individual element is simply arranged separately on the surface of the base body, but each element is formed on the head substrate by a semiconductor circuit manufacturing process or the like. It shows that it is integrally formed and manufactured on top.

  The “constant current” and “constant current source” in the present invention are a predetermined constant current applied to the recording element regardless of fluctuations in the number of simultaneously driven recording elements and a current source that supplies this current to the recording element. It means that. The current value that should be constant means that it includes a case where the current value is changed to a predetermined current value, that is, includes DHFC (foaming control).

<Description of Inkjet Recording Apparatus (FIG. 1)>
FIG. 1 is a schematic view of an ink jet recording apparatus which is a typical embodiment of the present invention. In FIG. 1, the lead screw 5004 rotates via driving force transmission gears 5009 to 5011 in conjunction with forward and reverse rotation of the carriage motor 5013. The carriage HC has a pin (not shown) that engages with the spiral groove 5005 of the lead screw 5004, and is supported by the guide rail 5003 as the lead screw 5004 rotates so as to reciprocate in the directions of arrows a and b. Is done. An ink jet cartridge IJC is mounted on the carriage HC. The ink jet cartridge IJC includes an ink jet recording head IJH (hereinafter referred to as a recording head) and an ink tank IT for storing recording ink.

  The ink jet cartridge IJC has a configuration in which the recording head IJH and the ink tank IT are integrated.

  Reference numeral 5002 denotes a paper pressing plate that presses the paper against the platen 5000 in the moving direction of the carriage. The platen 5000 is rotated by a conveyance motor (not shown) to convey the recording paper P. Reference numeral 5016 denotes a member that supports a cap member 5022 that caps the front surface of the recording head. Reference numeral 5015 denotes suction means for sucking the inside of the cap, and performs suction recovery of the recording head through the opening 5023 in the cap. Reference numeral 5017 denotes a cleaning blade, and reference numeral 5019 denotes a member that enables the blade to move in the front-rear direction, and these are supported by a main body support plate 5018.

  FIG. 2 is an external perspective view showing a detailed configuration of the ink jet cartridge IJC.

  As shown in FIG. 2, the ink jet cartridge IJC is composed of a cartridge IJCK that discharges black ink and a cartridge IJCC that discharges three color inks of cyan (C), magenta (M), and yellow (Y). ing. These two cartridges can be separated from each other and can be detached from the carriage HC independently.

  The cartridge IJCK includes an ink tank ITK that stores black ink and a recording head IJHK that discharges and records black ink. These cartridges have an integrated configuration. Similarly, the cartridge IJCC includes an ink tank ITC that stores three color inks of cyan (C), magenta (M), and yellow (Y), and a recording head IJHC that discharges and records these color inks. However, these are integrated. In this embodiment, the ink tank is filled with ink.

  In addition, the cartridges IJCK and IJCC can be used not only as an integral type, but also as a configuration in which the ink tank and the recording head are separated.

  The recording head IJH is used when the recording head IJHK and the recording head IJHC are collectively referred to.

  Further, as apparent from FIG. 2, the nozzle row for ejecting black ink, the nozzle row for ejecting cyan ink, the nozzle row for ejecting magenta ink, and the nozzle row for ejecting yellow ink are arranged side by side in the carriage movement direction. The The nozzle arrangement direction intersects the carriage movement direction.

  FIG. 3 is a perspective view showing a three-dimensional internal structure of the recording head IJHC that discharges three color inks.

  From FIG. 3, the flow of ink supplied from the ink tank ITK becomes clear. The recording head IJHC includes an ink channel 2C that supplies cyan (C) ink, an ink channel 2M that supplies magenta (M) ink, and an ink channel 2Y that supplies yellow (Y) ink. The ink tank ITK is provided with a supply path (not shown) for supplying each ink to each ink channel from the back side of the substrate.

  Ink channels 301C, 301M, and 301Y are provided corresponding to the electrothermal transducers (heaters) 401, and C ink, M ink, and Y ink are provided on the substrate through these ink channels, respectively. It is led to an electrothermal converter (heater) 401. When the electrothermal transducer (heater) 401 is energized through a circuit described later, heat is applied to the ink on the electrothermal transducer (heater) 401, and the ink boils. As a result, ink droplets 900C, 900M, and 900Y are ejected from the ejection ports 302C, 302M, and 302Y by the generated bubbles.

  In FIG. 3, reference numeral 1 denotes an electrothermal transducer to be described in detail later, various circuits for driving the memory, memory, various pads serving as electrical contacts with the carriage HC, and recording on which various signal lines are formed. A head substrate (hereinafter referred to as a head substrate).

  One electrothermal transducer (heater) and the MOS-FET that drives the electrothermal converter are collectively referred to as a recording element, and a plurality of recording elements are collectively referred to as a recording element unit.

  Although FIG. 3 shows the three-dimensional structure of the recording head IJHC that discharges color ink, the recording head IJHK that discharges black ink also has the same structure. However, the structure is one third of the configuration shown in FIG. That is, there is one ink channel, and the size of the head substrate is about one third.

  Next, a control configuration for executing the recording control of the recording apparatus described above will be described.

  FIG. 4 is a block diagram showing the configuration of the control circuit of the recording apparatus.

  In FIG. 4, 1700 is an interface for inputting a recording signal, 1701 is an MPU, and 1702 is a ROM for storing a control program executed by the MPU 1701. Reference numeral 1703 denotes a DRAM for storing various data (such as the recording signal and recording data supplied to the recording head). Reference numeral 1704 denotes a gate array (GA) that controls supply of print data to the print head IJH, and also controls data transfer among the interface 1700, MPU 1701, and RAM 1703.

  Further, reference numeral 1709 denotes a transport motor (not shown in FIG. 1) 1706 for transporting the recording paper P, 1706 denotes a motor driver for driving the transport motor 1709, and 1707 denotes a motor driver for driving the carriage motor 1710. Reference numeral 1705 denotes a head driver for driving the recording head IJH. This head driver outputs a logic signal as a control signal for variably setting a constant current value applied to the heater of the recording head IJH to a predetermined value, a control signal for controlling a switch provided in a voltage-current conversion circuit for generating a reference current, and the like. Is also output. When a signal for controlling this switch is generated inside the recording head, it is not necessary to transmit a signal from the recording apparatus main body.

  The operation of the control configuration will be described. When a recording signal enters the interface 1700, the recording signal is converted into recording data for printing between the gate array 1704 and the MPU 1701. Then, the motor drivers 1706 and 1707 are driven, and the recording head IJH is driven in accordance with the recording data sent to the carriage HC, and image recording on the recording paper P is performed.

  In this embodiment, the recording head configured as shown in FIG. 2 is used, and control is performed so that the recording by the recording head IJHK and the recording by the recording head IJHC do not overlap in each scanning of the carriage. In the case of color recording, the recording head IJHK and the recording head IJHC are driven alternately for each scan. For example, when the carriage performs reciprocal scanning, control is performed so that the recording head IJHK is driven in the forward scanning and the recording head IJHC is driven in the backward scanning. The drive control of the print head is not limited to such control, and the print operation is performed only by the forward scan, and the print head IJHK and the print head IJHC are driven by the two forward scans without carrying the recording paper P. Other controls may be performed.

  Next, the configuration and operation of the head substrate mounted on the recording head IJH will be described.

  FIG. 5 is a diagram illustrating a configuration of a heater driving circuit provided on the head substrate of the recording head IJH. In FIG. 5, the same components as those already described in FIG. 13 are denoted by the same reference numerals, and the description thereof is omitted.

FIG. 5 shows a reference current generation circuit 107 in addition to the reference voltage circuit 105, the voltage / current conversion circuit 104, and the current source block 106. The current source block 106 is made up of n current source blocks 106 ₁ - 106 _n having the same configuration. Further, a switch 108 is inserted in the voltage / current conversion circuit 104 in order to control energization of the reference current I _ref . The opening / closing time of the switch, that is, the time for supplying the reference current is controlled by the outside of the head substrate (that is, the main body of the recording apparatus).

  As the voltage source of the reference voltage circuit 105, it is desirable to output a voltage that is stable with respect to the power supply voltage and the temperature change. For example, a stable voltage with respect to the power supply power supply and the temperature change is obtained using a band gap voltage. .

Based on the reference current I _ref generated by the voltage-current conversion circuit 104, the reference current generation circuit 107 generates n reference currents IR1 to IRn. In this embodiment, whether or not the reference current I _ref is supplied is switched by controlling the switch 108. In addition to this, the n reference currents IR1 to IRn generated based on the reference current I _ref are switched simultaneously. Each of the n current source blocks includes _m constant current sources 103 _{1 to} 103 _m corresponding to m groups 106 including x heaters 101 and x switching elements 102.

The output terminals of the constant current sources 103 _{1 to} 103 _m provided for the groups 106-1 to 106 -m are connected to the common connection ends of the groups in which the heater 101 and the switching element 102 are connected in series in each group. Is done. Each constant current source is connected to the GND line 111.

In this embodiment, the switching element 102 is a MOSFET. Therefore, energization control to each heater is performed by turning ON / OFF the control signal applied to the gate of each MOSFET in each group. As a result, the output currents Ih1 to Ihm of the constant current sources 103 _{1 to} 103 _m provided for each group are supplied to a desired heater.

Here, as the constant current sources 103 _{1 to} 103 _m , constant current sources in which MOS transistors are operated in a saturation region are used. As a result, it is possible to arrange the power supply in a region where the circuit mounting density is high, such as in the vicinity of the heater.

  The head substrate is provided with a sensor 112 for detecting the temperature of the head, the output of which is output to the recording apparatus main body and used for constant current driving. In the recording apparatus main body, for example, MPU, G. A. Inputs the temperature of the head, and based on this, the time for supplying the reference current for constant current driving described in the following embodiments is determined.

  In FIG. 5, only one sensor is shown. However, the number of sensors may be plural. For example, each sensor may be provided for every n current source blocks. One or more may be provided. Further, in order to detect not only the temperature of the head but also the temperature around the printing apparatus, a sensor may be provided in the printing apparatus main body, and the time for supplying the reference current based on the sensor output can be controlled. Accordingly, the environmental temperature is interpreted as including not only the head temperature but also the temperature around the recording apparatus.

  Next, the operation of the heater drive circuit will be described.

Since the drive control of the m groups is performed by the same method, here, in the heater drive circuit shown in FIG. 5, x heaters 101 _{11 to} 101 _1x accommodated in the group 106-1 will be described as an example. .

  FIG. 6 is a diagram showing the time variation of the signal waveform of the control signal VGi applied to the gate of the switching element (MOSFET), the control signal Vs for controlling the switch 108, and the amount of current flowing through each heater.

  6A is a diagram showing a signal waveform of the control signal VGi applied to each switching element, and FIG. 6B shows a time change of the amount of current flowing through each heater.

  FIG. 7 is a diagram showing only the relationship between the control signals Vs and VG1 shown in FIG.

VG1 to VGx in FIG. 6A are control signals for controlling the x switching elements 102 _{11 to} 102 _1x to be turned on (short-circuited) or turned off (opened). Here, when the signal level of the control signal VGi is high (H), the corresponding switching element is turned on (conducted), and when the signal level is low (L), the corresponding switching element is turned off (non-conductive). Similarly, the switch 108 is turned on (conductive) when the signal level of the control signal Vs is high level (H), and the switch 108 is turned off (non-conductive) when the signal level is low level (L).

In the example shown in FIG. 6A, it is assumed that all the heaters 101 _{11 to} 101 _1x of the group 106-1 are sequentially driven.

According to FIG. 6 (A), the at time t = t1, the control signal Vs is a reference current I _ref to a high level flow, the reference current is supplied to the constant current source 103 _1. Since the gate control signals VG1 to VGx are all at the low level at t1 ≦ t <t2, the output of the constant current source 103 ₁ and the heaters 101 _{11 to} 101 _1x are open. For this reason, no current flows through any of the heaters 101 _{11 to} 101 _1x .

Next, at t2 ≦ t <t3, only the gate control signal VG1 becomes high level. Therefore only the switching element 102 ₁₁ is short-circuited, the constant current source 103 ₁ output current Ih1 flows through the heater 101 _11. In FIG. 6B, this is indicated by the output current Ih1-1 rising at t2 ≦ t <t3.

Then, it is t3 ≦ t the control signal VG1 is low level again, energization to the heater 101 ₁₁ is interrupted. Further, at t4 ≦ t, since the control signal Vs is at a low level, the energization of the reference current I _ref is interrupted, and the supply of the reference current to the constant current source 103 ₁ is stopped.

As described above, the reference current I _ref to t1 ≦ t <t2 immediately before energization to the heater 101 ₁₁ is supplied to the constant current source 103 _1. In t2 ≦ t <t3, the heater 101 ₁₁ is heated current is supplied to only the heater 101 _11. When energization to the heater 101 ₁₁ ends, the t4 ≦ t, supply of the reference current I _ref is interrupted. In this process, and it expands when heated ink in the vicinity of the heater 101 _11, ink is ejected from a nozzle heater 101 ₁₁ is disposed. Thereby, dots can be recorded.

Subsequently, the gate control signal VG2 is shorted switching element 102 ₁₂ becomes a high level, the constant current source 103 ₁ output current Ih1 is applied to the heater 101 _12. This is shown in FIG. 6 (B) by the output current Ih1-2 rising.

Similarly, the switching elements 102 _{11 to} 102 _1x are sequentially turned on when the gate control signal VGn sequentially goes high. Then, the output current Ih1 of the constant current source 103 ₁ is sequentially supplied to the heaters 101 _{11 to} 101 _1x . As a result, all the heaters 101 _{11 to} 101 _1x housed in the group 106-1 are driven.

Although the case where all the heaters 101 _{11 to} 101 _1x of the group 106-1 are sequentially driven has been described here, only heaters necessary for forming a desired dot are driven in an actual recording operation. Therefore, only when a desired heater is driven to record a dot, the control signal corresponding to the switching element becomes a high level.

  The operation described above is performed in the same manner for each heater accommodated in each of the groups 106-2 to 106-m. Thereby, energization control to each heater is performed, and any heater can be selectively driven from (x × m) heaters.

  Based on the basic control of the constant current driving described above, some embodiments for solving the problems mentioned in the section “Problems to be solved by the invention” of this specification will be described.

  8, FIG. 9, and FIG. 10 are diagrams for explaining the control for executing the constant current drive control according to the first embodiment.

In this embodiment, as shown in FIGS. 8 to 10, the reference current (I _ref ) is supplied longer than usual before recording or at the beginning of the recording operation under the head temperature at which ejection failure or ejection becomes unstable. The amount of heat generated in the reference current generation circuit 107 is increased. This keeps the head substrate warm. By keeping the temperature of the head substrate, the viscosity of the ink is lowered and it becomes easier to discharge.

  A method of controlling the supply time of the reference current will be specifically described with reference to FIG.

As shown in FIG. 7A, the rising time t = t1 of the control signal VS is before or simultaneously with the rising time t = t2 of the control signal VG1 applied to the switching element, that is, t1 ≦ t2. Fix to be. Further, under a low temperature environment, the control is performed so that the period Δt _3-4 from when the control signal VG1 becomes low level until the control signal VS starts to fall becomes longer.

  Thereby, it is possible to approach the discharge state at a normal temperature (25 ° C. or more).

FIG. 8 shows an example in which the environmental temperature is 10 ° C. In this case, the reference current (I _ref ) is supplied before recording and continues to be supplied for a while after the recording operation is started.

FIG. 9 shows an example in which the environmental temperature is 15 ° C. In this case, the reference current (I _ref ) is continuously supplied for a while as the recording operation starts.

FIG. 10 shows an example in which the environmental temperature is 20 °. In this case, at the initial stage of the recording operation, a pulse longer than the pulse of the reference current (I _ref ) supplied when ink can be ejected stably is supplied.

  The time for supplying such a reference current is defined by the opening / closing time of the switch 108, and the opening / closing time is controlled according to the head temperature detected by the sensor 112. Then, the reference current flows from the power supply line 110 to the GND line 111 for the time when the switch 108 is closed, and the reference current generation circuit 107 is driven for the time, and heat is generated from the circuit. As a result, the head substrate is heated by the heat generation.

  As described above, according to this embodiment, it is possible to perform good recording while suppressing occurrence of unstable ejection and defective ejection under a low temperature environment.

  FIG. 11 is a diagram for explaining control for executing constant current drive control according to the second embodiment.

  FIG. 11A shows a change in the temperature of the recording head when recording a high-density image (that is, recording with a high duty). As can be seen from this figure, the temperature change of the recording head is continuous and the change is not abrupt.

  FIG. 11B shows a recording head when a high-density image recording (high duty) and a low-density image recording (low duty) are performed with the reference current supply time constant regardless of the recording duty change. This shows the temperature change. As can be seen from this figure, the temperature change of the recording head is discontinuous, and when the recording duty changes discontinuously, the head temperature also changes rapidly. Hereinafter, the recording duty is simply referred to as duty.

  This is because there is a difference in temperature rise characteristics of the head substrate between high density image recording and low density image recording, and the ink discharge state is different. For this reason, dot formation for a high-density image is different from dot formation for a low-density image, and as a result, image quality may deteriorate.

  In this embodiment, when a high-density image and a low-density image are recorded together, the reference current supply time is set short when recording a high-density image to reduce the amount of heat generated by the reference current generation circuit 107. On the other hand, when recording a low density image, the supply time of the reference current is set long to increase the amount of heat generated in the reference current generation circuit 107. By doing so, as shown in FIG. 11C, the temperature of the recording head is set to a temperature characteristic (high temperature stable) close to a state where a high density image is always recorded (FIG. 11A). A constant recording state is maintained regardless of the duty.

  Note that the duty value is the same as the MPU, G.G. A. Can be obtained by analysis.

  As described above, according to this embodiment, the head temperature rise characteristic difference due to the recording duty is absorbed, and good recording can be performed even if the duty is different.

  FIG. 12 is a diagram illustrating control for executing constant current drive control according to the third embodiment.

  Characteristics reflecting manufacturing variations of the recording head are stored as rank characteristics by a nonvolatile memory (not shown) provided on the head substrate. When the recording head is mounted on the carriage, the recording apparatus reads rank characteristics from the nonvolatile memory and sets an appropriate reference current value for the recording head.

  FIG. 12A shows the supply time of the reference current when the set current value is low, while FIG. 12B shows the supply time of the reference current when the set current value is high.

According to this embodiment, as shown in FIG. 12B, for the recording head whose set current value is high, the supply time of the reference current (I _ref ) is set short, and the heat generation of the reference current generation circuit 107 is achieved. Reduce the amount. On the other hand, as shown in FIG. 12A, for the recording head whose set current value is low, the supply time of the reference current (I _ref ) is set long and the amount of heat generated in the reference current generation circuit 107 is set as shown in FIG. increase.

  As described above, according to this embodiment, by changing the supply time of the reference current according to the set current value, the temperature rise of each recording head is made substantially the same, and the difference in recording state due to individual differences of the recording heads is eliminated. be able to. Thereby, it is possible to eliminate the difference in the color of the recorded image due to the individual differences in the recording heads.

  In the above description, the first to third embodiments are individually described. However, the present invention is not limited thereto, and the head substrate having all the features included in the first to third embodiments, the recording head, and the head thereof. A recording apparatus using a recording head can also be configured.

1 is an external perspective view showing an outline of a configuration of a carriage peripheral portion of an ink jet recording apparatus that is a representative embodiment of the present invention. It is an external appearance perspective view which shows the detailed structure of the inkjet cartridge IJC. 3 is a perspective view illustrating a three-dimensional structure of a recording head IJHC that discharges three color inks. FIG. FIG. 2 is a block diagram illustrating a control configuration of the recording apparatus illustrated in FIG. 1. FIG. 3 is a diagram illustrating a configuration of a heater driving circuit provided on a head substrate of a recording head IJH. It is a figure which shows the time change of the signal waveform of the control signal VGi applied to the gate of a switching element (MOSFET), the control signal Vs which controls the switch 108, and the electric current amount which flows through each heater. FIG. 7 is a diagram showing only the relationship between the control signals Vs and VG1 shown in FIG. , , It is a figure explaining the control for performing the constant current drive control according to Example 1. FIG. It is a figure explaining the control for performing the constant current drive control according to Example 2. FIG. It is a figure explaining the control for performing the constant current drive control according to Example 3. FIG. FIG. 6 is a diagram illustrating a configuration of a heater driving circuit of a conventional recording head.

Explanation of symbols

101 _{11 to} 101 _mx heater 102 _{11 to} 102 _mx switching element (MOSFET)
103 _{1 to} 103 _m constant current source 104 voltage current conversion circuit 105 reference voltage circuit 106 current source block 107 reference current generation circuit 108 switch IJH recording head

Claims (11)

Multiple heaters;
A constant current source for generating a constant current used for driving the plurality of heaters;
A reference current generating circuit for generating a reference current for generating the constant current;
A switching element that drives the plurality of heaters by the constant current obtained by driving the constant current source according to a reference current generated by the reference current generating circuit;
A head substrate comprising: a switch for defining a time for generating the reference current; and an opening / closing time of the switch is controlled from the outside. A sensor for detecting the temperature;
The head substrate according to claim 1, wherein an opening / closing time of the switch is controlled according to a temperature detected by the sensor.   3. The head substrate according to claim 2, wherein the lower the temperature is, the longer the time during which the switch is closed and the reference current is generated. 4. It further has a non-volatile memory for storing characteristics reflecting manufacturing variations,
The head substrate according to claim 1, wherein an opening / closing time of the switch is controlled according to the characteristic.   5. The head substrate according to claim 4, wherein, according to the characteristic, the lower the reference current value, the longer the time for generating the reference current by closing the switch. 6.   A recording head using the head substrate according to claim 1.   The recording head according to claim 6, wherein the recording head is an ink jet recording head that performs recording by discharging ink.   A head cartridge comprising an ink tank for storing ink to be supplied to the ink jet recording head according to claim 7.   A recording apparatus that performs recording by discharging ink onto a recording medium using the ink jet recording head according to claim 7 or the head cartridge according to claim 8. Means for analyzing recording data transmitted from the outside and obtaining a duty of recording by the recording head;
The recording apparatus according to claim 9, further comprising means for controlling an opening / closing time of the switch according to the duty.   The recording apparatus according to claim 10, wherein the control unit performs control so that when the duty is low, the switch is closed and the time for generating the reference current is lengthened.

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